We faced the same problem with ss316 plant piping after hydro test. We observed several leakages during precom work after hydro. The reason was attributed to Micro biological corrosion resulted due to improper/incomplete water draining and dry/inert lay up.
All the effected lines are replaced with newmaterial and effected lines are undergone Ozone treatment and lay up before precommissionig and Plant startup.
regards
Reddysr
Reddysr
On Fri, Mar 19, 2010 at 3:32 PM, Desai Jignesh (Mumbai - Piping) <J.J.Desai@ticb.com> wrote:
The concentration of the chlorides by evaporation of hydrotest water remaining in the piping system may cause stress corrosion cracking of the piping near welds. Provisions must be made to ensure that hydrotest water is fully drained and/or flushed from the piping system. The water used for the hydrostatic test, apart from the requirements as to chloride content, shall be free from sediment or undissolved solids of any typehydrotest water containing up to 20 mg/kg chlorides (20 parts per million or less) may be used for the pressure test of ASS.Regds/Jignesh
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of biju psl
Sent: Friday, March 19, 2010 4:43 PM Subject: [MW:4582] corrosion problem in TP321 pipes after hydrotesting
Hi,We have a 2"Sch-40 A312TP321 piping .We tested the above line 4 months before partially and accepted. Same line when we tested again now it started leaking at several locations(welds and pipe)We tested the water used for testing the line and found that the chloride content is 120ppmIs it possible that just because of this high chloride content the line starts leaking within 3 months?best regards,BIJU--
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